Nếu \(x = \frac{a}{b};y = \frac{c}{d}\,\,\left( {b,d \ne 0} \right)\) thì tích x.y bằng 

A. \(\frac{{a.d}}{{b.c}}\)

B. \(\frac{{a.c}}{{b.d}}\)

C. \(\frac{{a + c}}{{b + d}}\)

D. \(\frac{{a + d}}{{b + c}}\)